Water purification devices which purify at slow rate, such as those which use the distillation and the reverse-osmosis processes, deliver water into a storage tank or reservoir from which the water is dispensed. The same is true in regard to systems which use bottled water and water filter dispensing coolers. The water, however, may be easily contaminated with bacteria by contact with air on the storage and dispensing mechanisms, or merely by sitting stagnant in the reservoir. This is particularly true with bottled water cooler dispensers and those units that are used as replacements for bottled water cooler dispensers since the tanks are non-pressurized, and therefore must be vented to permit water to be dispensed by gravity flow.
A known method for eliminating bacterial contamination is the use of ultra-violet (“UV”) light. The light energy from a UV lamp is germicidal, because UV light penetrates microbial organism's protective membrane layer and photochemically damages the DNA structure, disabling its self-reproducing capability and rendering the cell lifeless.
UV light is in the region of the electromagnetic spectrum that lies between visible light and X-rays. The ultra-violet spectrum ranges from 100 nm to 400 nm wave lengths, with the optimum effective range between 250 nm to 270 nm. The UV lamp is commonly housed in a protective sleeve of quartz which is similar to a test tube that allows ultra-violet transmission and separates the lamp and wiring from the water surrounding the lamp. The quartz sleeve also helps the UV lamp to maintain its optimal operating temperature of approximately 105° F. Factors that determine a UV system's effectiveness include the intensity of the lamp, the exposure time of the water to the ultra-violet rays and the water transmission rate which is determined by the quality and color of the water.
The typical storage reservoir for water purification units is not usually suitable for effective UV application. In gravity-filled storage reservoirs, there must be a method for controlling the water level within the reservoir, and typically a float valve or switch is used. With a UV bulb inside the reservoir, a float valve or switch would normally act as an obstruction to the UV light rays, and provide a sheltered location for bacterial contamination to grow. A typical size and storage capacity for a point of use reservoir is in the order of approximately 4 to 6 gallons, which is required to compensate for the slow recovery rate of the purification system.
Since UV has a limited effective transmission distance, the physical dimensions of a 4 to 6 gallon storage reservoir have not been suitable for effective UV application. A very high intensity UV lamp would be required in such cases and this would heat the chilled water thereby reducing the efficiency and effectiveness of the chilling process. Moreover, UV degrades most plastics, and typically in large reservoirs, floats and switches are constructed of plastic.
A typical point of use and bottled water dispenser reservoir is divided into two compartments by an internal baffle that separates the water which has been cooled from the water that is still at room temperature. Two faucets are used, one for dispensing room temperature water and the other for dispensing chilled water. The baffle that separates the cold and room temperature sections blocks UV rays from reaching one of the compartments in such systems.
It has been observed in U.S. Pat. No. 6,139,726 that the known prior art has not solved any of these problems. Although U.S. Pat. No. 6,139,726 is a large improvement over the prior art, there still remains a need to reduce the cycling on and off of the UV bulb as well as the “on” time of the bulb as these factors degrade the life of the bulb. Co-pending U.S. application Ser. No. 10/000,874, incorporated herein by reference, addresses this issue and others.
However, even with these improvements, there sometimes exists a need to utilize a larger wattage of UV lamp. Furthermore, a longer bulb would also provide a longer exposure time with thin film flow around the UV lamp and the quartz sleeve. A need exists to provide UV energy to areas previously inaccessible to the UV rays. A need also exists to detect leaks into the quartz sleeve about the UV lamp. Furthermore, a need exists to provide protection to a user in the event of breakage of a sleeve and/or lamp.